In an attempt to make this answer more worthy of the Accept I'd like to arbitrarily address an edge case that might come up. Suppose you have RuleDelayed expressions and you wish to reverse them:

rules = {a :> 1 + 1, b :> 2 + 2, c :> 3 + 3};
rules ~Reverse~ 2

{2 :> a, 4 :> b, 6 :> c}

Note that e.g. 1 + 1 became 2; for the sake of the illustration let's consider this unacceptable. Then we would need to wrap the left-hand-side in HoldPattern. A direct attempt using @@@ fails because the anonymous Function does not hold its arguments (by default):

HoldPattern[#2] -> # & @@@ rules

{HoldPattern[2] -> a, HoldPattern[4] -> b, HoldPattern[6] -> c}

One could add a HoldAll Attribute to the function but usually replacement patterns are simpler:

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